Serological screening for tuberculosis in the community: an evaluation of the Mycodot procedure in an African population with high HIV-2 prevalence (Republic of Guinea-Bissau).

The immuno-dot-blot assay MycoDot, which detects lipoarabinomannan (LAM) antibodies, was evaluated for the serological diagnosis of active pulmonary tuberculosis in patients in a rural community in the Republic of Guinea-Bissau. Sera from 269 adults (age > 15) and 33 children (age < 5) were assayed for antibodies in a blind manner and the results compared to the clinical status of tuberculosis. The assay had a specificity and a sensitivity of 92.4% and 63.0% respectively, when applied to the adult population. In HIV-2 infected individuals (27/269), the specificity and sensitivity of the assay were similar, 94.7% and 62.5% respectively. The assay did not provide high sensitivity for the diagnosis of tuberculosis in children. Sera from patients with leprosy cross-reacted with the antigen of the assay. It is concluded that this easily performed assay may be useful for the presumptive diagnosis of tuberculosis in adult populations in rural areas of developing countries where routine screening is not readily available.

Serological screening for tuberculosis in the community: an evaluation of the Mycodot procedure in an African population with high HIV-2 prevalence (Republic of Guinea-Bissau)

The immuno-dot-blot assay MycoDot, which detects lipoarabinomannan (LAM) antibodies, was evaluated for the serological diagnosis of active pulmonary tuberculosis in patients in a rural community in the Republic of Guinea-Bissau. Sera from 269 adults (age > 15) and 33 children (age < 5) were assayed for antibodies in a blind manner and the results compared to the clinical status of tuberculosis. The assay had a specificity and a sensitivity of 92.4 per cent and 63.0 per cent respectively, when applied to the adult population. In HIV-2 infected individuals (27/269), the specificity and sensitivity of the assay were similar, 94.7 per cent and 62.5 per cent respectively. The assay did not provide high sensitivity for the diagnosis of tuberculosis in children. Sera from patients with leprosy cross-reacted with the antigen of the assay. It is concluded that this easily performed assay may be useful for the presumptive diagnosis of tuberculosis in adult populations in rural areas of developing countries where routine screening is not readily available.

Development of a polymerase chain reaction dot-blotting system for detecting cutaneous tuberculosis.

For a definitive diagnosis of cutaneous tuberculosis the demonstration of mycobacteria is essential, but this is generally not possible in skin lesions. Routinely available techniques have poor sensitivity and are time consuming, therefore, delaying the institution of timely therapy. The high sensitivity and speed of polymerase chain reaction (PCR) for the detection of infectious agents has prompted investigators to use this technique for the detection of Mycobacterium tuberculosis in body fluids such as cerebrospinal fluid or pleural fluid. In the present study, PCR was used to examine punch biopsy specimens from the affected skin of 10 patients with clinical diagnoses of tuberculosis verrucosa cutis, lupus vulgaris, scrofuloderma, papulonecrotic tuberculide and erythema induratum. A control group of 20 patients included individuals having skin manifestations with definite clinical diagnoses other than cutaneous tuberculosis, such as leprosy, fungal mycetoma, chronic bullous disease of childhood and pemphigus vulgaris. The PCR amplified products were dot hybridized with a probe which was random prime labelled with 32P. The results were compared with routine microbiological and histological findings. Among the test group, six of 10 (60%) were positive for M. tuberculosis by PCR, although their histopathology showed non-specific chronic inflammation with no definite diagnosis. Microbiological investigations, including acid-fast bacillus smear and culture, were positive in a single case of scrofuloderma. All patients in the control group were negative by PCR for M. tuberculosis. The data indicate that the combination of dot hybridization with PCR markedly increased the sensitivity and specificity of PCR. This may be a useful tool in the diagnosis of tuberculosis when conventional methods fail.

DOT-ELISA for detection of phenolic glycolipid PGL-Tb1 and diacyl-trehalose antigens of Mycobacterium tuberculosis.

A DOT-ELISA method for detection of 2,3-diacyl-trehalose (DAT, previously referred to as SL-IV antigen) and triglycosyl phenol phthiocerol di-mycocerosate (PGL-Tb1) antigens from Mycobacterium tuberculosis is described. The method enabled the detection of both antigens in 14 clinical isolates of M. tuberculosis from different geographic origins; the presence of the glycolipids was confirmed by chemical analysis. It was therefore concluded that the synthesis of both of these compounds is characteristic of the species.

The dot-ELISA test for the detection of anti-PGL-1 IgM in leprosy patients and their contacts.

1. Since dot-ELISA has recently been reported to be a sensitive, simple and fast method, we have compared it with the conventional microplate ELISA method. Sera of 124 leprosy patients, 136 household and professional contacts, and 92 controls were tested for antibodies against a Mycobacterium leprae antigen using dot-ELISA on nitrocellulose membrane filters and microplate ELISA. 2. The sensitivity of the two techniques was similar for multibacillary patients, but dot-ELISA was less sensitive for paucibacillary patients although it was more specific (100%) than ELISA (93.4%). 3. Of 21 household contacts that gave a response by ELISA, 3 were also positive by dot-ELISA; one of these 3 developed indeterminate leprosy 12 months later and the other was diagnosed as borderline lepromatous after 28 months. 4. These data indicate that dot-ELISA has a high specificity and can be a useful tool in field evaluation.

The dot-ELISA test for the detection of anti-PGL-1 IgM in leprosy patients and their contacts

Since dot-ELISA has recently been reported to be a sensitive, simple and method, we have compared it with the conventional microplate ELISA method. Sera of 124 leprosy patients, 136 household and professional contacts, and 92 controls were tested for a antibodies against a Mycobacterium leprae antigen using dot-ELISA on nitrocellulose membrane filters and microplate ELISA. The sensitive of the techniques was similar for multibacillary patients, but dot-ELISA was less sensitive for paucibacillary patients although it was more specific (100%) than ELISA (93,4%). Of 21 household contacts that gave a response by ELISA, 3 were also positive by dot-ELISA; one of these 3 developed indeterminate leprosy 12 months later and the other was diagnosed as borderline lepromatous after 28 months. These data indicate that dot-ELISA has a high spedificity and can be a useful tool in field evaluation